D316 - Decision numbers are reserved under a lock

Status: decided Date: 2026-08-27

./bin/orbistoun decide "<title>" claims the next decision number under a mkdir lock and writes a reservation before any body exists. The gate refuses duplicate numbers and reservations left unfilled.

Why: several sessions write decisions at once, and "read the highest number and add one" races over the minutes spent writing the body. Source cites decisions by number, so a collision makes every citation ambiguous. mkdir is atomic on every platform this runs on. An abandoned reservation reads like a recorded decision.

Rejected:

• Reading the highest number: races between sessions.
• Relying on the duplicate check alone: fires after citations already point at both.